Patti Stouter just tested her hyper-wattle wall system that’s she’s building at her home in New York. She’s published the results on her Hyper-wattle proposal at the $300 House design competition. She’s been in the top three consistently and there’s a very good chance she’ll win first place. I believe her project is the best and deserves to win. Please vote if you have a chance. Like I said earlier, every vote for one of the sustainable designs is a vote against the industrialized solutions.
“Only a hint of how strong these wattle walls might be. We just placed almost 170 lbs/ linear foot on a 30″ high wall portion made of tiny 6″ diameter wattles. This is the one seen in the middle right on plate 6, with half to 5/8 inch diameter diagonal branches tied in about every 12″. The wattle appears very dry, and we used some room heat and a fan to hasten drying. It has a base layer of earthen plaster that is still damp, and has some cracking. So this could be stronger with a finish plaster layer that is totally dry. [Ed.: Yes, much stronger.]
At 90 lbs per linear foot we could measure less than one percent compression. Roof weights for an ordinary asphalt shingle roof with framing and plywood on a 10’x10′ building (3 x 3m) would be about 4 lbs per linear foot.
If two percent compression is acceptable, the building should be able to hold up this type of roof with a snow load of 20 lbs, what my region of southern NY gets.
This needs more testing, and lots of discussion of wind forces and shear strength. But for regions without snow, does anyone else agree with me that this kind of wall will be able to hold up a light roof? [Ed.: I say yes, especially when you consider the finished plaster will be thicker. Roof loads will be transferred through the rigid plaster skins, not the wattles.]
It takes one large straw bale to fill enough wattle for 2.7′ length of wall 5′ high. That’s a bit of straw, but if one can build after the harvest, and straw is a waste material, it might be worthwhile. [Ed.: Baled straw isn’t required. Most areas have some type or grass, straw or reeds that will work.] I like straw-bale housing, but this dipped clay technology might allow people in very humid regions to have a less mold-susceptible house. [Ed.: And the narrow walls take up less space.]
I’ve rushed this first test to have some data before the Jovoto contest is over. I want to put a finish plaster on this little panel and then compress it till it falls apart. I also have a larger wall panel that I hope to do a shear test on eventually, when it’s dry. Today I’m going to do the second layer of plaster on it.
The side photo shows that this little wattle wall wasn’t even perfectly straight. I hope to be able to include some wattle panels in the shed I’m building now for gable walls. I’m going to test out doing a trash wattle panel flat on the ground and see if straw-clay plaster stiffens it up much.
Personally I like traditional earthbag because it’s simple and fool-proof. But there are many places that some different materials are more easily accessed than subsoil.”